1. Field of the Invention
The present invention relates to a spatial information detection system for receiving light from a target space, into which an intensity-modulated light is being irradiated, to detect information about the target space.
2. Description of the Related Art
In the past, the technique of detecting spatial information such as a distance to an object existing in a target space by receiving light from the target space, into which an intensity-modulated light is being projected, and determining a phase difference in modulation component between the projected light and the received light has been utilized. For example, this technique is disclosed in PCT International Publications Nos. WO96/15626 and WO2004/008175, and it is essential to use a detection device basically composed of a light emitting source for projecting light intensity-modulated with a predetermined modulation period to the target space, a photodetector having a photoelectric converting portion configured to receive light from the target space, and to generate electric charges corresponding to a received light amount, and an evaluation portion for detecting spatial information of the target space from a change between the light projected from the light emitting source and the light received by the photodetector.
By the way, because this kind of detection device projects the intensity-modulated light into the target space, there is an inconvenience when detecting the spatial information from a common target space by use of a plurality of detection devices. That is, when lights are simultaneously projected to the target space from the detection devices, it becomes difficult to distinguish the light projected into the target space from the light emitting source of one of the detection devices from the light projected from another one of the detection devices into the target space. In brief, because each of the detection devices cannot extract only the light projected by its own light emitting source from the lights projected to the target space, there causes a problem that the detection accuracy of the spatial information deteriorates.